Blocking factors in sera of breast cancer patients

Abstract

In previous studies, we have demonstrated that serum blocking factors (SBF) from sera of breast cancer patients was specific in our Leukocyte Adherence Inhibition assay (LAI).34 To elucidate the nature of SBF, we have investigated the antigen-antibody complex by precipitation of immune complexes (I.C.) with polyethylene glycol (PEG). Specific and nonspecific blocking activities of sera obtained from breast cancer patients were investigated using the LAI and PHA-induced lymphocyte blastogenesis (PHA Blastogenesis) assays. I.C. precipitated in PEG, were utilized to test simultaneously the blocking capacity of these complexes and the corresponding serum. Blocking activity of sera and corresponding I.C. correlated in 20 out of 24 (83%) experiments in the LAI assay and 16 out of 19 (84%) experiments in the PHA Blastogenesis assay. When immune complexes from breast cancer patients were quantitatively compared with normal donors and benign breast patients, a significantly higher yield of protein concentration was obtained. Furthermore, I.C. of benign breast patients was also higher than normal controls. When 10 of the 28 I.C. were further fractionated into Ig (Retentate) and antigen containing component (Filtrate) by ultrafiltration after acid treatment, neither of these components manifested blocking. When reconstituted at a ratio of Ig:antigen = 1:1, blocking activity was again restored in 3 out of 3 in LAI and in 3 out of 4 in blastogenesis. In two experiments, I.C. with negative blocking was readily converted to a positive blocking state with the addition of a small amount of antigen. I.C. also demonstrated specificity in blocking activity and the degree of blocking activity depended on the concentration of I.C. in cultures. Evidence obtained suggests that specific and nonspecific serum blocking factors are related to I.C. but not to the fractionated components of Ig nor antigen. Cancer 43:838–847, 1979.